US7070612B1 - System and method for bringing hypothermia rapidly onboard - Google Patents

Abstract

An intravenous heat exchange catheter and/or an external cooling pad/bladder can be used to maintain hypothermia in, e.g., a cardiac arrest patient, but to accelerate the cooling process the patient first can be infused with cold saline before the opportunity arises to connect the catheter or pad to the patient.

Description

This is a continuation-in-part of U.S. patent application Ser. No. 11/064,187, filed Feb. 23, 2005, from which priority is claimed.

FIELD OF THE INVENTION

The present invention relates generally to therapeutic hypothermia.

BACKGROUND OF THE INVENTION

Intravascular catheters have been introduced for controlling patient temperature. Typically, a coolant such as saline is circulated through an intravascular heat exchange catheter, which is positioned in the patient's bloodstream, to cool or heat the blood as appropriate for the patient's condition. The coolant is warmed or cooled by a computer-controlled heat exchanger that is external to the patient and that is in fluid communication with the catheter.

For example, intravascular heat exchange catheters can be used to combat potentially harmful fever in patients suffering from neurological and cardiac conditions such as stroke, subarachnoid hemorrhage, intracerebral hemorrhage, cardiac arrest, and acute myocardial infarction, or to induce therapeutic hypothermia in such patients. Further, such catheters can be used to rewarm patients after, e.g., cardiac surgery or for other reasons. Intravascular catheters afford advantages over external methods of cooling and warming, including more precise temperature control and more convenience on the part of medical personnel.

The following U.S. patents, all of which are incorporated herein by reference, disclose various intravascular catheters/systems/methods: U.S. Pat. Nos. 6,419,643, 6,416,533, 6,409,747, 6,405,080, 6,393,320, 6,368,304, 6,338,727, 6,299,599, 6,290,717, 6,287,326, 6,165,207, 6,149,670, 6,146,411, 6,126,684, 6,306,161, 6,264,679, 6,231,594, 6,149,676, 6,149,673, 6,110,168, 5,989,238, 5,879,329, 5,837,003, 6,383,210, 6,379,378, 6,364,899, 6,325,818, 6,312,452, 6,261,312, 6,254,626, 6,251,130, 6,251,129, 6,245,095, 6,238,428, 6,235,048, 6,231,595, 6,224,624, 6,149,677, 6,096,068, 6,042,559.

Surface cooling may be less optimally used. For example, externally applied cooling pads are disclosed in U.S. Pat. Nos. 6,827,728, 6,818,012, 6,802,855, 6,799,063, 6,764,391, 6,692,518, 6,669,715, 6,660,027, 6,648,905, 6,645,232, 6,620,187, 6,461,379, 6,375,674, 6,197,045, and 6,188,930 (collectively, “the external pad patents”), all of which are incorporated herein by reference.

Regardless of the modality of cooling, it is believed that the sooner a patient is cooled after ischemic insult, the better the therapy. The present invention recognizes that many patients will have their first encounter with health care personnel in ambulances, prior to being afforded the opportunity for critical care such as controlled maintenance of hypothermia. Thus, it would be advantageous, as understood herein, to provide a means to bring cooling on board to patients as soon as possible.

SUMMARY OF THE INVENTION

A system for controlling patient temperature includes a closed loop heat exchange catheter configured for placement in the circulatory system of a patient to exchange heat with the blood of the patient. The system also includes a source of cold fluid, with the cold fluid being colder than normal body temperature and infusable from the source into the patient without using the catheter.

The catheter may be configured for percutaneous advancement into the central venous system of the patient. The catheter can carry coolant that is not infused into the bloodstream of the patient.

In another aspect, a method for treating a patient using hypothermia includes injecting cold saline into the venous system of the patient while the patient is located in an ambulance or in an emergency room of a hospital. Then subsequently hypothermia is maintained in the patient using an external heat exchange pad or an intravascular heat exchange catheter while the patient is in an operating room of a hospital or an intensive care unit of a hospital.

In yet another aspect, a method for treating a patient includes infusing into the patient's venous system a cold fluid having a temperature lower than a temperature of the patient to cause the fluid to mix with the blood of the patient and thereby to cool the patient. The method also includes engaging a cooling apparatus with the patient to maintain a desired hypothermic condition in the patient.

In additional embodiments, a system for controlling patient temperature includes a closed loop heat exchange catheter configured for placement in the circulatory system of a patient to exchange heat with the blood of the patient, and an external heat exchange bladder configured for exchanging heat with the skin of a patient. The system also includes a heat exchange system in a single housing and engageable with both the catheter and the bladder.

In non-limiting implementations of this last embodiment, the housing can include a sensor which detects when the heat exchange system is connected to the bladder, and potentially to the catheter as well, to provide a signal to a controller in the housing. Additionally, a controller may be in the housing and receive a patient temperature signal from a BTT sensor. Further, an IV bag can be supported on the housing for infusing cold saline directly into the bloodstream of a patient.

Continuing to summarize non-limiting implementations, the heat exchange system may include a coolant loop configured for exchanging heat with a working fluid loop associated with the catheter. The coolant loop may also be configured for direct fluid communication with the bladder. Or, the heat exchange system can include a coolant loop having a coldwell, with the catheter being associated with a catheter working fluid loop including a catheter coil disposable in the coldwell and with the bladder being associated with a bladder working fluid loop including a bladder coil disposable in the coldwell. Both working fluid loops may be associated with respective pumps. The heat exchange system may also include an internal reservoir for priming the bladder, and may control both the catheter and bladder simultaneously. The heat exchange system can include a refrigerant loop including a compressor and one or more heat exchangers communicating with the compressor.

In another aspect, a heat exchange system includes a coolant loop, at least a first working fluid loop in thermal communication with the coolant loop and an intravascular heat exchange catheter associated with the first working fluid loop such that working fluid circulates through the heat exchange catheter without entering the patient's bloodstream when the catheter is positioned in the bloodstream. At least one external heat exchange member is configured for placement against a patient's skin to heat or cool the skin. The external heat exchange member is configured for heat transfer using the coolant loop.

In another aspect, a method for patient temperature control includes providing a heat exchange system, and engaging an intravascular heat exchange catheter with the system and with a patient to exchange heat with the patient. The method also includes engaging at least one bladder with the system and placing the bladder against the patient's skin to exchange heat with the patient.

In other aspects, a patient temperature control system includes at least one bladder through which working fluid can flow. The bladder is positionable against the skin of a patient, and a skin conditioning hydrogel can be disposed between the bladder and the skin.

In another aspect, a patient temperature control system includes at least one bladder through which working fluid can flow, with the bladder being configured as the front of a garment and having a trunk portion and two opposed limb portions that can drape over the patient.

In another aspect, a patient temperature control system includes at least one bladder through which working fluid can flow. The surface of the bladder facing away from a patient when the bladder is positioned against the skin of the patient is backed by a foam that conforms to pressure caused by the weight of the patient.

The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing two modalities of controlled hypothermia maintenance in a patient, along with an apparatus for quickly reducing patient temperature;

FIG. 2 is a flow chart of logic;

FIG. 3 is a diagram of a single heat exchange chassis system that supports both an external cooling bladder and an intravascular temperature control catheter;

FIG. 4 is a schematic diagram showing that the heat exchange system can have two heat exchangers in parallel with one compressor;

FIG. 5 is a schematic diagram of an alternate system;

FIG. 6 is a cross-section of a non-limiting quick disconnect feature as would be seen along theline6—6 inFIG. 5;

FIG. 7 is a schematic diagram of an alternate system; and

FIG. 8 is a schematic diagram of an alternate system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially toFIG. 1, a system is shown, generally designated10, that includes aheat exchange catheter12 that is in fluid communication with a cathetertemperature control system14.

In accordance with present principles, thesystem10 can be used to induce therapeutic hypothermia in apatient16 using a catheter in which coolant circulates in a closed loop, such that no coolant enters the body. While certain preferred catheters are disclosed below, it is to be understood that other catheters can be used in accordance with present principles, including, without limitation, any of the catheters disclosed in the following U.S. patents, all incorporated herein by reference: U.S. Pat. Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673, 6,149,676, 6,231,594, 6,264,679, 6,306,161, 6,235,048, 6,238,428, 6,245,095, 6,251,129, 6,251,130, 6,254,626, 6,261,312, 6,312,452, 6,325,818, 6,409,747, 6,368,304, 6,338,727, 6,299,599, 6,287,326, 6,126,684. Thecatheter12 may be placed in the venous system, e.g., in the superior or inferior vena cava.

Instead of or in addition to thecatheter12, thesystem10 may include one ormore pads18 that are positioned against the external skin of the patient16 (only onepad18 shown for clarity). Thepad18 may be, without limitation, any one of the pads disclosed in the external pad patents. The temperature of thepad18 can be controlled by apad controller20 in accordance with principles set forth in the external pad patents to exchange heat with thepatient16, including to induce therapeutic mild or moderate hypothermia in the patient in response to the patient presenting with, e.g., cardiac arrest, myocardial infarction, stroke, high intracranial pressure, traumatic brain injury, or other malady the effects of which can be ameliorated by hypothermia.

To cool the patient while awaiting engagement of thecatheter12 and/orpad18 with the patient,cold fluid22 in a coldfluid source24 may be injected into the patient and in particular into the patient's venous system through apathway26. Without limitation, thepathway26 may an IV line, thesource24 may be an IV bag, and the fluid22 may be chilled saline, e.g., saline at the freezing point or slightly warmer. Or, the source may be a syringe, and the saline can be injected directly into the bloodstream of the patient.

Now referring toFIG. 2, atblock28 the patient presents with symptoms indicating that the application of hypothermia is appropriate. For instance, the patient may have cardiac arrest, and may be resuscitated. Or, the patient may present with myocardial infarction or stroke or other malady.

Atblock30,cold saline22 is immediately (in the case of cardiac arrest patients, immediately after resuscitation) injected into the patient's bloodstream, preferably at a venous site, using thesource24. This can occur in, e.g., an ambulance on the way to the hospital for further temperature management, and/or in the hospital emergency room. Hypothermia treatment including the establishment and maintenance of mild or moderate hypothermia subsequently is effected atblock32 using thecatheter12 and/orpad18, typically in the operating room or intensive care unit of a hospital, although in some hospitals the step atblock32 may begin while the patient is still in the emergency room or even while the patient is still in the ambulance.

The above three modalities of cooling—intravascular closed loop catheter, external pad/bladder, and cold saline bolus infusion—may be supported by a single housing.

With greater specificity,FIG. 3 shows details of one non-limiting single-chassis heat exchange system, generally designated100, which includes a single heatexchange system housing102 holding all or portions of three fluid loops. Specifically, arefrigerant loop104 exists in which refrigerant flows between acompressor106 and at least oneheat exchanger108. Exiting theheat exchanger108, the refrigerant passes through aCP valve110 to acondenser112, which condenses the refrigerant. Therefrigerant loop104 may be replaced by a thermoelectric cooling loop in which the fluid is air passing over and cooling a TEC element.

In theheat exchanger108, the refrigerant expands to cool a coolant in acoolant loop114, which is in thermal but not fluid contact with therefrigerant loop104. The coolant may be water, propylene glycol, a mixture thereof, or other suitable coolant. Also included in thecoolant loop114 is aheater116 for heating the coolant to, e.g., re-warm a patient, and acoolant pump118 to circulate the coolant through thecoolant loop114. The coolant pump may be a magnetically-coupled non-displacement pump, or a positive displacement pump.

FIG. 3 shows that the coolant flows into a chamber defined by acoldwell120, which may be the highest point in the system. A catheterfluid loop coil122 may be disposed in thecoldwell120 in thermal but not in fluid contact with the coolant. The catheterfluid loop coil122 defines part of a workingfluid loop124 through which a working fluid such as saline flows. The fluid in the workingfluid loop124 circulates, under the influence of a workingfluid pump126, which can be a peristaltic pump, through an intravascularheat exchange catheter128 without exiting the catheter into the bloodstream. The working fluid exchanges heat with the coolant in thecoldwell120. Asaline bag130 may be provided in the workingfluid loop124 for priming purposes, and anair trap132 may also be provided to prevent any air that might exist in the workingfluid loop124 from entering thecatheter128. The entire workingfluid loop124 may be provided as a standalone catheter start-up kit, with the catheterfluid loop coil122 disposed by medical personnel in thecoldwell120 and with thecatheter128 then being advanced into the vasculature of a patient to exchange heat with the patient. Additional details of thenon-limiting system100 may be found in the present assignee's U.S. Pat. Nos. 6,146,411, 6,581,403, and 6,529,775, all of which are incorporated herein by reference, and in U.S. patent application Ser. No. 10/944,544, filed Sep. 17, 2004, also incorporated herein. The above patents further disclose non-limiting ways in which a controller/power supply133 controls various of the components above to heat or cool the working fluid as necessary to achieve a user-set target temperature. Apatient temperature sensor133acan send a patient temperature signal to thecontroller133 as shown. Thesensor133amay be any suitable sensor including, without limitation, a brain temperature tunnel (BTT) sensor to sense the temperature through thin peri-occular skin of a sinus, which represents the temperature of the brain.

Still referring toFIG. 3, in lieu of placing the catheterfluid loop coil122 in thecoldwell120 and thecatheter128 in the patient, a bladdercooling loop coil134, which is part of abladder fluid loop136, may be disposed in thecoldwell120. Abladder fluid pump138, which can be a positive displacement pump, circulates working fluid, which could be tap water or saline or other appropriate fluid, through theloop136. Included in theloop136 is an externally-appliedbladder140 through which the working fluid flows to cool a patient. Thebladder140 may be any suitable cooling device such as a conformal pad or a mattress that is placed against the skin, including any of the devices referred to previously. An adhesive or non-adhesive hydrogel and/or a silver sulphur diazene cream or zinc paste may be disposed between the bladder and patient. Or, a skin conditioning hydrogel such as glycerol in sorbolene can be used. The bladder itself may be configured as the front of a shirt or trousers, i.e., with a trunk portion and two opposed limb portions that can drape over the patient. The surface of the bladder that faces away from the patient can be backed by a NASA foam that conforms to pressure caused by the weight of the patient to reduce the risk of bedsores.

Asaline bag142 may be provided in theloop136 for priming. Also, a three-way stopcock144 can be provided as shown to isolate thebag142. Theloop136 may be controlled by a separate bladder controller/power supply146, which may communicate with thecontroller133 if desired.

AnIV pole147 may be mounted on thehousing102 and may support anIV bag148, for infusing cold saline in the IV bag directly into the bloodstream of the patient as shown. Acoil149 may be provided in communication with the IV bag. Thecoil149 may be disposed in thecoldwell120 to cool saline in coil, which can circulate under the influence of apump149a.

FIG. 4 shows that for greater heat exchange power, acompressor150 may circulate refrigerant through twoheat exchangers152,154, either in parallel with each other or with one of the heat exchangers isolated by means of a computer-controlledsolenoid valve156. The arrangement shown inFIG. 4 could be used in lieu of the arrangements shown in the other figures herein.

FIG. 5 shows thecoolant loop portion200 of analternate system202, which in all essential respects is identical to thesystem100 shown inFIG. 3 with the following exceptions. Coolant such as water may flow, under the influence of acoolant pump204, through aheat exchanger206 and a computer-controlled three-way valve208, which either sends the coolant to acoldwell210 to exchange heat with the coil of an intravascular catheter as described above, or to abladder loop212 that includes an externalheat exchange bladder214 as shown. A primingreservoir216, which can be internal to the chassis of thesystem202, may be provided for priming thebladder214 with coolant, it being understood that in some embodiments the coldwell itself can be used for priming instead, in which case an additional three-way valve between the coldwell and first three-way valve208 could be required for establishing the appropriate fluid flow control.

In any case, as shown inFIG. 5 thebladder214 is connected to asupply line218 and areturn line220, with thelines218,220 terminating inrespective bladder fittings222,224 that engagerespective system fittings226,228 on the chassis of thesystem202. Preferably, the fittings are quick disconnect fittings that provide an indication of engagement and disengagement to the controller (not shown) of thesystem202 for establishing the position of the three-way valve208 for catheter or bladder operation as appropriate. Thus, inFIG. 5 the coolant loop supplies either the coldwell for exchanging heat with the working fluid circuit of the intravascular catheter, or it supplies the bladder directly.

It is undesirable that the heat exchanger freeze during, e.g., priming. Accordingly, when the system detects the bladder being connected, it can maintain system fluid temperatures above the freezing point. In any case, to avoid skin damage it is preferred that when the bladder is used the coolant temperature be maintained between four and forty two degrees Celsius.

A non-limiting example of quick disconnect fittings (using224,228 as examples) is shown inFIG. 6. As shown, the bladder fitting224 may be circumscribed by acollar230, and as the bladder fitting224 is advanced into the system fitting228, thecollar230 deflects aball232 that is reciprocally disposed in the wall of the system fitting228 and that is urged inwardly (toward the bladder fitting224) as shown by aspring234. As theball232 deflects, it actuates asensing element236 on the system fitting228 to provide an “engaged” signal to the system controller, which can then reconfigure the user interface and/or control parameters used for establishing patient temperature. Or, the ball and spring can be omitted and the collar seat against the sensing element when the fittings are engaged, to actuate the sensing element. Other arrangements known in the art may be used. Thesensing element236 may be an electrical contact or other suitable element known in the art. It is to be understood that the catheter start-up kit shown inFIG. 3 may also be connected to the system using such fittings, so that in any of the embodiments herein, the controller “knows” which device or devices, catheter and/or bladder, is connected.

FIGS. 7 and 8 show alternate embodiments in which abladder300 is part of a bladder workingfluid loop302 that includes abladder coil304 disposable in abladder coldwell306, it being understood that the catheter-related working fluid loop shown inFIG. 3 with separate catheter coldwell and catheter working fluid loop pump is also provided in a system that includes the refrigerant loop and working fluid loop shown inFIG. 3. In essence, in the systems ofFIGS. 7 and 8 two separate working fluid loops are provided, one for the external cooling bladder and one for the intravascular catheter, with both loops being controlled by a common controller, e.g., the controller303 shown inFIG. 3. In any case, a bladder workingfluid loop pump308 provides the motive force for circulating the working fluid. Either an external saline bag310 (FIG. 7) can be provided for priming through a three-way stopcock312, or a reservoir314 (FIG. 8) that is internal to the system chassis can be provided. In both cases, asupply line316 to thecoil304 and areturn line318 from the bladder300 (or from thestopcock312 when one is used as shown inFIG. 7) terminate in quick-disconnect fittings320,322 as shown, for operation as described above to alert the system controller to whether the bladder is connected. In the embodiments shown inFIGS. 7 and 8, since two separate working fluid loops are provided, both the catheter and the bladder can be simultaneously controlled by the controller to heat or cool a patient. Or, if simultaneous catheter/bladder use is not required, the bladder loop may not include its own coldwell and pump but rather can use a single coldwell that services either catheter and bladder.

While the particular SYSTEM AND METHOD FOR BRINGING HYPOTHERMIA RAPIDLY ONBOARD as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. All structural and functional equivalents to the elements of the above-described preferred embodiment that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”.

Claims (19)

1. A system for controlling patient temperature, comprising:

a closed loop heat exchange catheter configured for placement in the circulatory system of a patient to exchange heat with the blood of the patient;

an external heat exchange bladder configured for exchanging heat with the skin of a patient; and

a heat exchange system engageable with both the catheter and the bladder, wherein the heat exchange system includes at least one coolant loop having a coldwell, the catheter being associated with a catheter working fluid loop including a catheter coil disposable in the coldwell, the bladder being associated with a bladder working fluid loop including a bladder coil.

2. The system ofclaim 1, wherein the heat exchange system includes a housing holding at least one sensor sensing the fluid flow engagement of the heat exchange system with at least one of: the bladder, and the catheter, the sensor providing a signal to a controller in the housing.

3. The system ofclaim 1, comprising a controller receiving a patient temperature signal from a BTT sensor.

4. The system ofclaim 1, comprising at least one IV bag supported on a housing of the system for infusing cold saline through an IV line and directly into the bloodstream of a patient.

5. The system ofclaim 1, wherein the heat exchange system includes at least one coolant loop, the coolant loop configured for exchanging heat with a working fluid loop associated with the catheter, the coolant loop also being configured for fluid communication with the bladder.

6. The system ofclaim 1, wherein the heat exchange system includes at least one refrigerant loop including a compressor and at least one heat exchanger communicating with the compressor.

7. The system ofclaim 6, comprising two heat exchangers in fluid flow parallel with each other.

8. The system ofclaim 1, wherein both working fluid loops are associated with respective pumps.

9. The system ofclaim 8, wherein the heat exchange system includes an internal reservoir for priming the bladder.

10. The system ofclaim 1, wherein the heat exchange system simultaneously controls respective temperatures of respective fluids flowing through both the catheter and bladder.

11. A beat exchange system, comprising:

a coolant loop;

at least a first working fluid loop in thermal communication with the coolant loop;

at least one intravascular heat exchange catheter associated with the first working fluid loop such that working fluid circulates through the heat exchange catheter without entering the patient's bloodstream when the catheter is positioned in the bloodstream; and

at least one external heat exchange member configured for placement against a patient's skin to heat or cool the skin, the external heat exchange member being configured for heat transfer using the coolant loop.

12. The system ofclaim 11, wherein the external heat exchange member is associated with a second working fluid loop, the second working fluid loop exchanging heat with the coolant loop.

13. The system ofclaim 11, wherein the external heat exchange member is configured for connecting to the coolant loop to receive coolant therefrom.

14. The system ofclaim 11, wherein the coolant loop is embodied in a heat exchange system contained in a single housing and engageable with both the catheter and the external heat exchange member.

15. The system ofclaim 14, wherein the housing includes at least one sensor sensing the fluid flow engagement of the heat exchange system with at least one of: the external heat exchange member, and the catheter, the sensor providing a signal to a controller in the housing.

16. The system ofclaim 14, comprising a controller in the housing and receiving a patient temperature signal from a BTT sensor.

17. The system ofclaim 14, comprising at least one IV bag supported on the housing for infusing cold saline directly into the bloodstream of a patient.

18. The system ofclaim 14, wherein the heat exchange system simultaneously controls respective temperatures of respective fluids flowing through both the catheter and bladder.

19. A method for patient temperature control, comprising:

providing a heat exchange system;

engaging an intravascular heat exchange catheter with the system and with a patient to exchange heat with the patient; and

engaging at least one bladder with the system and placing the bladder against the patient's skin to exchange heat with the patient.

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